viral gastroenteritis

Viral gastroenteritis results from viral infection and destruction of mature enterocytes at the tips of intestinal villi, leading to malabsorption and secretion of fluid/electrolytes, causing osmotic and secretory diarrhea. Key pathogens: Rotavirus (double-stranded RNA, Reoviridae) - most common cause of severe diarrhea in children <5 worldwide, damages villous enterocytes leading to decreased absorption of Na+/glucose; prevented by live oral vaccine (RotaTeq, Rotarix). Norovirus (ssRNA, Calicivirus) - most common cause of foodborne outbreaks and gastroenteritis in adults in developed countries, highly contagious via fecal-oral route, fomites, and aerosolized vomitus; causes rapid onset vomiting and diarrhea, no long-term immunity due to antigenic variation. Other causes: Adenovirus (serotypes 40/41, non-enveloped dsDNA), Astrovirus.

Clinical presentation: acute onset (12-48 hrs incubation) watery, non-bloody diarrhea, nausea/vomiting, low-grade fever, abdominal cramps, myalgias. Distinguish from bacterial gastroenteritis (which more often causes bloody diarrhea, high fever, and is caused by invasive organisms like Shigella, Salmonella, Campylobacter, EHEC).

Diagnosis primarily clinical; stool studies (PCR panels) if severe, immunocompromised, or outbreak setting. Management is supportive: oral or IV rehydration, electrolyte repletion; antiemetics as needed. Antibiotics not indicated. Complications: dehydration (especially dangerous in infants/elderly), electrolyte imbalances.

Key boards associations: Rotavirus vaccine reduced hospitalization rates significantly; contraindicated if history of intussusception. Norovirus outbreaks classically linked to cruise ships, contaminated shellfish, and person-to-person spread in close quarters; resistant to alcohol-based sanitizers, requires bleach-based disinfection.